T-cell lymphoma that involves the skin is generally known as cutaneous t-cell lymphoma (CTCL). The term CTCL encompasses a number of disorders, including mycosis fungoides (MF), which is the most common form of CTCL. Sézary syndrome (SS) is an advanced, variant form of mycosis fungoides, characterized by the presence of malignant lymphocytes in the blood. See “Getting the Facts” monograph for “Cutaneous T Cell Lymphoma” published by the Lymphoma Research Foundation, 115 Broadway Suite 1301, New York N.Y. 10006 (last update January 2013). No specific diagnostic or prognostic markers exist to enable early diagnosis of MF, SS and CTCL. The pathogenesis of CTCL is unknown and there are no therapeutic targets available for disease-specific therapies. Because no specific diagnosis is possible, CTCL is often confused with other inflammatory dermatoses, such as psoriasis or eczema, and patients often live with the disease for years before a correct diagnosis is established. If diagnosed early, CTCL patients have a longer lifespan, but the survival rate goes down as CTCL reaches advanced stages. Thus, a diagnostic test that could easily confirm the presence of CTCL early in disease course is needed.